Boron carbide ceramics have excellent properties such as light weight, high strength (for example, bending strength of 323 to 430 MPa), high hardness (for example, Vickers hardness of 27.4 to 34.3 GPa), high melting point (for example, 2400° C.), high modulus (for example, Young's modulus of 455 GPa), corrosion resistance, chemical stability, and favorable thermal and electric conductivity. FIG. 10 is a phase diagram of the carbon-boron system (hereinafter, a carbon system is referred to as “C”; and a boron system is referred to as “B”). The ordinate indicates the temperature (° C.) and the abscissa indicates the content ratio of C relative to B.
Boron carbide ceramics are currently attracting attention as high-temperature structural materials for use in, for example, engine components.
Although ceramics obtained are superior in thermal resistance, wear resistance, corrosion resistance and the like to many metal materials, ceramics have the drawback of “brittleness” that can affect the strength of the material.
Sintered ceramic composites have been used to provide increased productivity and improved mechanical properties under ordinary and high-temperature environments. As a result, there is a demand for methods for manufacturing such composites.
Methods for reducing brittleness may involve improving the sintered density of ceramics through improved manufacturing processes. For example, i) the ceramics may be mixed with a metal, ii) the particles may be dispersed, or iii) the ceramics may be reinforced with fibers.
Mixing ceramics with a metal produces ceramics having a high toughness due to their utilization of the ductility, i.e., the plastic deformation, of the composite metal. As a result, such ceramics may be unsuitable for high-temperature structural materials. Different kinds of particles may be dispersed in a ceramic matrix. Reinforcing of ceramics with fibers can result in a ceramic matrix having improved toughness, which can allow for a reduction in the weight of the ceramics.
Fiber-reinforced ceramics, which contain a principal phase (matrix, also referred to as a mother phase) and fibers as constituents, allow for the production of composite ceramics that exhibit a target performance by combining the matrix and the fibers as constituents.